Add a bootable ROM disk to your vintage compact Macintosh! Replace the startup sound, change the Happy Mac icon, edit the ROM disk, or tweak the ROM code behavior. The Mac ROM-inator Kit replaces the stock 64K or 128K of ROM in a compact Macintosh with a full 1 MB of flash memory. Once installed, the flash ROM’s contents can be updated from within the running Macintosh, allowing for crazy customization experiments. The Mac ROM-inator supports the Macintosh Plus, Mac 512Ke, 512K, and 128K.
The Mac ROM-inator is great for breathing new life into your old compact Mac. Customized startup sounds add a touch of fun, and the ROM disk provides fast and convenient boot-ups. A simple GUI tool on the Mac makes it easy to modify common sections of the ROM, including the ROM disk contents. For power users, binary editing of the ROM image opens new possibilities like altering the built-in fonts and modifying the system startup routines.
The kit includes preprogrammed flash chips with these ROM changes as defaults. Any of them can be changed by updating the flash memory.
- Startup beep is replaced by a glass “ping”
- Happy Mac icon is replaced by a Mac wearing sunglasses
- Pirate icon is displayed while waiting to load the ROM disk
- ROM disk image including System 6, Mac Write, Mac Draft, and eight games
- 128K ROM code turns a Mac 128K or 512K into a 128Ke or 512Ke
- Mac ROM-inator Kit assembly instructions
- Utility program for in-system ROM updating: Flash Tool
- Data files for in-system ROM updating: zip archive, stuffit archive. Includes a variety of startup sounds, Happy Mac icons, disk images, and ROM code versions for use with ROM-inator.
The Macintosh Plus, 512Ke, 512K, and 128K all support the Mac ROM-inator. Due to the way the ROM-inator works, some software running on a ROM-inator-equipped Mac 128K or 512K may think it’s running on a Mac Plus.
Mac 128K Owners: The Flash Tool utility program requires 192K of RAM, so it can’t run on an unmodified Mac 128K. The ROM-inator hardware works on the Mac 128K, but modifying the flash ROM contents requires a second Macintosh or an external EPROM programmer.
When first powered on, the Macintosh will play a customized startup sound, and display a “pirate Macintosh” icon. To boot from the ROM disk, press and hold the R key on the keyboard for a few seconds. If R is not pressed, the Macintosh will boot normally from an attached SCSI disk, or wait for a floppy disk to be inserted.
The 1 MB flash ROM includes 132K for ROM code, 28K for a custom startup sound, and up to 864K for a ROM disk image. The preprogrammed flash chips contain ROM code based upon the Mac Plus ROM. If used with a Macintosh 128K or 512K, it will turn them into a 128Ke or 512Ke. This will also give those machines native HD20 support, for use with Floppy Emu in HD20 hard disk emulation mode.
The utility program Flash Tool can update the flash ROM from within the running Mac. Alternatively, the flash chips can be removed from their sockets and reprogrammed using a standard EPROM programmer.
To use Flash Tool, simply select the ROM area and the data file to use for the update. The program will verify that the data file is the correct size for the area to be updated. After about sixty seconds, it’s done!
The ROM code area contains 128K of patched code from the Macintosh Plus ROM, with a 4K ROM disk driver appended. The disk image for the ROM disk can be any standard Macintosh disk image up to 864K in size, such as image files used with Floppy Emu or Mini vMac.
The startup sound is stored in raw 22 kHz 8-bit unsigned format. The free audio tool Audacity can convert WAV or MP3 files to this format. By default the sound will play for 0.66 seconds at startup, but with an additional ROM modification this can be changed to any interval between 0 and 1.3 seconds.
Creating a New ROM Disk
Want to create a new ROM disk image, with a collection of your own favorite software? Follow the ROM disk tutorial to create a new image, then use Flash Tool to update the ROM-inator’s flash memory.
Alternative Happy Mac Icons
The data files include about a dozen different varieties of Happy Mac icons – see the downloads section above. Each alternate Happy Mac is part of a ROM code file that contains the modified icon. To use one of these icons on your Mac, use Flash Tool to program the corresponding ROM code file to the ROM-inator’s flash memory.
If you’re comfortable editing binary files in a hex editor, you can design your own Happy Mac icons. The happy face is stored as a 20 byte raw bitmap, beginning at offset $FD2 (hex) in the ROM code file. The outline of the Macintosh icon is defined elsewhere, so only the 16 x 10 rectangle within the “screen” area of the icon can be modified using this method.
Fancy a shot at reverse-engineering? How are your 68000 assembly skills? Start with this commented source listing of the stock Mac Plus ROM to identify areas that might be interesting to hack. The listing also shows the address and assembled byte values for each line, so you can cross-check it against the ROM code image files included with the ROM-inator downloads. Identify an interesting data table or piece of code, and use your favorite binary editor to modify it. Then update ROM-inator’s flash memory with Flash Tool to put your new ROM changes into action.
The commented source listing is for the stock Mac Plus ROM (the 128K ROM), not the modified ROM that’s included with the ROM-inator kits. The primary difference is that the “ROM code” section of the ROM-inator’s flash memory is 132K, not 128K. The extra 4K holds the device driver code for the ROM disk. The remaining 128K also contains patches to load the device driver, and to enable modified startup sounds and Happy Mac icons.
- What Macintosh models are supported?
Macintosh Plus, 512Ke, 512K, and 128K.
- How difficult is the kit to assemble?
All the components are 0.1 inch through-hole parts. Some closely-spaced headers are slightly tricky, but nothing the average solder-aware hobbyist should have trouble with.
- Must I solder wires to the CPU?
That’s the recommended method for the most secure installation. It’s possible to use IC test clips instead, but the limited clearance between the logic board and the Macintosh chassis frame can make clips difficult to use.
- Does this require a special boot disk or software?
No, everything is in ROM. The Flash Tool utility can be used to update ROM contents, but is not required for normal operation.
- Can I write to the ROM disk?
No, the ROM disk is read-only. However, its contents can be modified between reboots using Flash Tool.
- What if I want to return my Mac to the stock setup?
You can update the flash memory with a stock ROM image, to return the Mac to stock behavior while leaving the ROM-inator board installed. Alternatively, you can remove the ROM-inator board entirely and replace the original ROM chips. The chips are in sockets on the Mac logic board, so no permanent modifications are required.